PCL(4k)-PEG(3k)-COOH is a block copolymer containing polycaprolactone (PCL) (hydrophobic) and PEG (hydrophilic). Upon dispersion in water, the polymer self-assembles to form micelles with PCL core and PEG shell. The core can be used as reservoir for hydrophobic drugs while the shell can provide protection from degradation (enzymatic/hydrolysis). The acid (COOH) is reactive with amino molecule in the presence of activator, such as HATU/EDC. Reagent grade, for research purpose.